This invention relates to a zooming structure of an interchangable camera lens and, most particularly, to a zooming structure of the kind set forth above which allows both telephotographing and closeup photographing of the camera.
There is a known interchangable camera lens for telephotographing in which a zooming operation is performed by sliding an operation ring straightly in the axial direction thereof while a focusing operation is performed by rotating the operation ring about the axis thereof. Such an interchangable camera lens of straight zoom type has advantages due to easy operation and quick photographing compared with another type of interchangable camera lens of rotary zoom type in which the zooming and focusing operations have to be performed respectively by rotation of separate members. Accordingly, the interchangable camera lenses of straight zoom type are now becoming very popular in the field.
In one example of the interchangable camera lens of straight zoom type, four groups of lenses are provided in which a lens group for variable magnification is operatively connected with a cam slot in a cylindrical cam sleeve to move in the axial direction thereof in proportion i.e. rectilinearly, to the rotary movement of the cam sleeve, while another lens group for focus compensation is operatively connected with another cam slot in the same cam sleeve to move out of proportion, i.e. non-rectilinearly, to the rotary movement of the cam sleeve. The cylindrical cam sleeve is operatively connected with an operation ring outside the camera lens in such a manner that when the operation ring is slided in the axial direction thereof, the cam sleeve is rotated about the axis thereof. Thus, the zooming operation for telephotographing is performed by straightly sliding the operation ring.
In the above type of interchangable camera lens having four groups of lenses, it is known that in case the lens group for focus compensation only is moved back in the axial direction while the lens group for variable magnification takes the most advanced position where the focusing distance is minimum for the widest telephotographing of the camera, the photographing state of the camera lens is changed from the telephotographing state into the closeup photographing state.
However, in the conventional interchangable camera lens, although the zooming operation for the telephotographing could be made by straightly sliding an operation ring in the axial direction thereof, the closeup photographing has to be adjusted by rotating the operation ring or another separate operation ring. Also, in order to change the photographing state from telephotographing to closeup photographing, a mechanical locking means has to be released to allow the rotation of the operation ring for the closeup photographing. Thus, the mechanism and structure of the conventional interchangable zoom lens have been complicated. Furthermore, the operation to change the photographing state from telephotographing to closeup photographing has been troublesome.
Accordingly, an object of the present invention is to provide an improved zooming structure of interchangable camera lenses in which the photographing state can be changed from the telephotographing state to closeup photographing state by straightly sliding an operation ring in the axial direction thereof without manipulating any locking means.
Another object of the present invention is to provide an improved zooming structure of interchangable camera lenses which is very simple in structure and easy and reliable in operation.
A further object of the present invention is to provide an improved zooming structure of interchangable camera lens in which the sliding movement of an operation ring becomes very smooth without contacting a rotating cam sleeve.